Abstract Detail

An initial study of the interaction between auxin and antheridiogen during Ceratopteris richardii gametophyte development.

Our research focuses on the role of auxin in the development of gametophytes of the fern Ceratopteris richardii. Early growth of the gametophyte is generated by an apical meristem, and female/hermaphrodites generate a second lobe by activating a lateral meristem on either side of the prothallus, while males do not activate a lateral meristem. Our studies with auxins and auxin-regulating compounds (Gregorich, M.*, and Fisher, R. H. (2006) Auxin regulates lateral meristem activation in developing gametophytes of Ceratopteris richardii. Canadian Journal of Botany 84: 1520-1530.) show that exogenous auxin represses lateral meristem development, auxin is necessary for limiting the initiation of a lateral meristem to one side of the prothallus, and auxin polar transport is required for the proper timing of lateral meristem initiation. Interestingly, some gametophytes grown in the presence of exogenous auxin or auxin-regulating compounds phenocopy sexual determination mutants. In this poster we present an initial attempt to unravel the potential interactions between auxin-mediated gametophyte development and the sexual determination of gametophytes by culturing gametophytes on auxin-regulating compounds in combination with antheridiogen, the male-inducing hormone of Ceratopteris richardii. Gametophytes cultured on NAA, a synthetic auxin, lack lateral meristems as do male gametophytes and differ principally from males in that they produce many rhizoids, and few or no antheridia. Gametophytes cultured on NAA and antheridiogen also lack lateral meristems, and produced numbers of antheridia and rhizoids which were intermediate between gametophytes grown on NAA or antheridiogen alone. Gametophytes cultured on PCIB, which interferes with auxin action, sometimes produce lateral meristems, and make fewer antheridia and fewer rhizoids than male gametophytes. Gametophytes cultured on both PCIB and antheridiogen make fewer rhizoids and more antheridia than gametophytes cultured on PCIB or antheridiogen alone. These results indicate that there is some interaction between auxin regulation and sexual determination in Ceratopteris richardii.